無遲滯效應之聚合物穩定藍相液晶探討

Abstract

聚合物穩定藍相液晶(polymer-stabilized blue phase liquid crystals or PSBP-LCs)之遲滯效應一直是光電元件應用上需克服的難題。在本論文中，我們藉由升降溫來減少PSBP-LCs間之晶體轉向不匹配，成功實現無遲滯現象之PSBP-LCs。主要物理機制利用藍相液晶長晶之晶體轉向需滿足玻璃基板之最小表面自由能且長晶速率與溫度相關，在降溫過程中，較適合系統之藍相液晶晶體轉向其單一立方結構(unit cell)數目增加且增加速率較其他晶體轉向快。而升溫時，較適合系統之藍相液晶晶體轉向其立方結構變少的速度反而較其他晶體轉向慢，故透過控制升降溫循環過程，藍相液晶之單晶可增大且減少PSBP-LCs晶體間之轉向不匹配。我們亦成功實現無遲滯效應之In-plane switching (IPS) 聚合物穩定藍相液晶顯示器。此研究為藍相液晶之光電元件開啟了新的一扇窗。

The hysteresis in polymer-stabilized blue phase liquid crystals (PSBP-LCs) hinders the applications of photonics devices. In this thesis, a hysteresis-free PSBP-LCs is demonstrated using thermal recycling to reduce the mismatch of orientations among crystals of PSBP-LCs. The mechanism is: the preferred orientation of BP-LC during the crystal growth satisfies the minimum surface free energy of substrates and the speed of the crystal growth depends on temperature. During cooling, the numbers of the unit cell with a preferred orientation of BP-LCs are enlarged faster than the others. During heating, the numbers of the unit cell with a preferred orientation of BP-LCs decreases slower than the others. By manipulating the thermal recycling, the size of a single crystal of BP-LCs increases and then the mismatch of orientations among crystals of PSBP-LCs reduces. A hysteresis-free in-plane switching liquid crystal display can be realized. This study opens a new window for blue-phase-LC based photonic devices.